NASA has successfully blasted two probes into space on a landmark lunar exploration mission to scout water sources and landing sites in anticipation of sending mankind back to the moon in 2020.

The launch marked "America's first step in a lasting return to the moon," a NASA official said moments after a rocket carrying the probes launched at 5:32 pm (2132 GMT), one day after the US space agency scrubbed the shuttle Endeavour launch for the second time in a week because of a nagging hydrogen fuel leak.

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The liftoff of the dual LRO and LCROSS missions atop an Atlas V rocket from Florida's Cape Canaveral Air Force Station, adjacent to Kennedy Space Center, took place one month shy of the 40th anniversary of NASA's historic first landings on Earth's natural satellite in 1969.

Americans have been the only astronauts to walk on the moon -- with the last such outing in 1972 -- and the new mission is the first step on the long journey to launch manned missions further into our solar system, to the planet Mars and beyond, from lunar colonies.

US President Barack Obama has said the program, dubbed the Constellation project, needs to be reviewed, but so far has not cast doubt on its goals.

"The robotic mission will give us information we need to make informed decisions about any future human presence on the moon," program manager Todd May told reporters earlier this week.